water pipe freezes but why doesn't borehole pump burn out?

[Ruraldweller]

Hi, my rural cottage is not on mains water and uses a borehole with a pump. In the cottage roof is a holding tank with an electric switch connected to the float. This automatically turns on the pump as required. The water passes through an outhouse before entering the cottage, using a standard, well lagged copper pipe. However, in the very cold weather, this pipe freezes.

Can anyone tell me why the pump doesn't burn out when this happens. Because of the size of the holding tank it is sometimes several days before we know the inlet pipe has frozen.

Thanks

 

[digdilem]

Borehole pumps are generally submerged in the water, and cooled by that water. It will shorten its life by being run for long periods, especially against a blockage as this obviously raises the pressure and makes the impellor and motor work harder, but it shouldn't overheat and 'burn out'.

I've lost four 2.2 hp top-mounted pumps through burnout and frost damage over the past two years, but have now switched to a submerged pump to prevent both of those problems. (Not borehole, but feeding hoses half a km away)

 

[Agile]

Its an odd feature of pumps that most types actually work less hard if the outlet is closed off.

One that I operated some while ago took 8 Amps when the valve was closed and that increased to 14 Amps when the valve was opened. ( Three phase delta so three times that current.

Tony